NA,K-ATPASE IN SEVERAL TISSUES OF THE RAT - TISSUE-SPECIFIC EXPRESSION OF SUBUNIT MESSENGER-RNAS AND ENZYME-ACTIVITY

The relative contents of Na,K-ATPase subunit mRNAs in rat renal cortex, ventricular myocardium, skeletal muscle (hind limb), liver and brain (cerebrum) were measured. Expressed per unit DNA, mRNA(alpha1) content was approximately 2-fold greater in the kidney and brain as compared to either heart, skeletal muscle or liver. The hierarchy of mRNA(alpha2) expression was brain > skeletal muscle > heart, whereas mRNA(alpha3) was restricted to brain. Beta1 subunit mRNA content in both kidney and brain exceeded the abundance of liver mRNA(beta1) by approximately 7-fold. In all tissues examined, the combined abundances of the alpha subunit mRNAs exceeded the content of mRNA(beta1). The hierarchy of Na,K-ATPase activity expressed per unit DNA was brain > kidney > skeletal muscle = heart > liver. The sum of mRNA(alpha) as well as mRNA(beta1) content, expressed per g of tissue, was highest in brain and kidney. A statistically significant correlation between mRNA(beta1) content and Na,K-ATPase activity was evident.